This invention relates to the determination of one or more spatial parameters of an object. The invention has particular application in the field of surveying, navigation, earth-moving equipment control, robotics, aeroplane landing, and so on.
Current surveying and navigational measurements fall into two categories: measurement of distance and measurement of both angular elevation and azimuth angle. Distance can be measured by means of the yardstick or, more commonly, nowadays, by measuring the time taken for an electromagnetic signal to be sent from a transmitter and reflected by the object back to the transmitter. The distance travelled by the signal is then equal to twice the distance between the transmitter and the object, thereby enabling the distance easily to be calculated. This method, forms the basis of radar measurements. Measurements of angular elevations are usually made using theodolytes or variations thereof.